1. Field
This disclosure relates generally to making semiconductors, and more specifically, to making semiconductor devices using a stress memorization.
2. Related Art
A stress memorization technique (SMT) that includes forming a SMT film over a transistor has been found in which stress can be created and transferred to an underlying transistor channel by a thermal treatment, and the stress can be retained by the underlying transistor even after the SMT film has been removed. The removal of the SMT film after the stress transfer is for exposing transistor source/drain/gate regions for contact silicidation. It is well known in the art that proper channel stress can enhancement transistor carrier mobility. For example, N-type transistor is enhanced by tensile stress which can be induced by SMT. Although there are benefits, one problem that has been found in using SMT films is that the gate dielectric tends to grow in the channel along the border of the channel during the SMT processes. This adversely impacts transistor performance.
Thus there is a need for a technique that induces stress to transistor devices with the SMT but avoiding or reducing the problem described above.